Detergent products comprising anionic and/or nonionic surfactants which are particularly suitable for fabric washing generally have a tendency in use to produce excessive foam. This can be a problem particularly with drum-type washing machines, and it is accordingly usual to include an antifoam agent in the detergent formulation to reduce or eliminate this tendency to produce excessive foam.
Excessive foam derived from detergent products containing anionic and/or nonionic surfactants can for example be controlled to a limited extent by the addition of soap, or by the incorporation of certain oils, such as hydrocarbons or silicone oils, or particles such as hydrophobic silica, or mixtures of such materials.
It has, for example, been proposed in GB No. 1 571 501 (Unilever) to provide a detergent powder composition comprising a lather controller consisting of a polyvalent salt of an alkyl phosphoric acid, such as calcium stearyl phosphate, and a hydrocarbon. The lather controller can be sprayed onto the detergent powder prior to packaging.
Although such antifoams are highly effective in reducing the tendency of a freshly manufactured detergent product to produce excessive foam, there is still a substantial risk that the antifoam activity will diminish on storage in a detergent powder. This is believed to be due to migration of some of the antifoam active substances, particularly those of an oily nature, into the surrounding powder or even the packaging material. This can happen more rapidly when such powders are stored at temperatures above room temperature (20.degree. C.), and after a period of storage of a few weeks the activity of the antifoam agent can be severely impaired.
It is accordingly desirable to incorporate the antifoam agents in the detergent powder during manufacture in a form in which they are protected against premature deactivation during storage, so that their effectiveness in controlling excessive foam production, both at low and at high washing temperatures, is not diminished.
We have now discovered that deactivation of the antifoam ingredient during storage in a powder detergent product can be substantially reduced or eliminated altogether, and sensitivity to foam control at both low and high wash temperatures maintained, if the antifoam ingredient is a particulate material comprising antifoam material supported in an oil-impervious matrix formed by a mixture of free fatty acid and soap. Premature loss during storage of any oily antifoam material by migration from within the particles into the dry detergent powder product or even into the packaging, is thereby restricted or eliminated. By this means, antifoam material is retained within the particle until contacted with water, for example during the washing of fabrics, when its release can then be triggered to produce effective foam control. The effectiveness of the antifoam ingredient is thereby retained until it is needed at the point of use.
GB No. 1 507 312 (Unilever) relates to coated particulate material in which the coating comprises an alkali metal salt of a long chain fatty acid having 8 to 22 carbon atoms and a free fatty acid having 8 to 22 carbon atoms in a weight ratio within the range of 1:4 to 2:1. Amongst the several particulate materials which are listed as being suitable for coating are foam inhibitors, but the specification does not identify any particulate substances that can be employed in foam control. There is no suggestion that the coating material is suitable for encapsulating oily antifoam materials, thus preventing premature loss which would lead to deactivation during storage, while at the same time ensuring that the oily materials are readily available when required for foam control.
EP No. 210 721A (Dow Corning), published on 4 Feb. 1987, discloses antifoam granules comprising silicone oil carried on a water-insoluble matrix of fatty acid and/or fatty alcohol melting at 45.degree.-80.degree. C.: in the wash liquor the silicone oil is released by melting of the matrix material.